Since an organic light emitting diode (OLED) display device has advantages of light weight, foldability, wide viewing angle, low cost, and the like, it has been more and more widely used.
FIG. 1 schematically shows a structure of a conventional top emitting type OLED display unit in the prior art. As shown in FIG. 1, the OLED display unit includes a first electrode 10 provided on a substrate 1. The first electrode 10 is an anode and is a reflective electrode. The first electrode 10 is used as a pixel electrode in the display device, and is made of a conductive metal with a high work function. The OLED display unit further includes a second electrode 30 arranged on a light emitting material layer 20. The second electrode 30 is a cathode and is made of a conductive metal with a low work function. Unlike an anode electrode, the formation of a cathode electrode requires the application of a common voltage to a pixel unit. Therefore, in order to facilitate the application of the common voltage to all pixel units, the structure of cathode electrodes is in the form of a common electrode connected as a whole for all of the pixel units.
An auxiliary electrode 40 is further formed on the cathode. This is because, in a large sized display device, an increased wire resistance of the cathode covering all pixel electrodes (anode) generates a voltage drop, which results in uneven light emission of the respective pixel units and an increased power consumption of the display panel, and the voltage drop of pixel electrodes can be prevented by providing the auxiliary electrode 40.
A main problem in the structure of the above-mentioned light emitting display unit is that the auxiliary electrode 40 is formed after the light emitting material layer 20, and thus the production of the auxiliary electrode 40 may lead to certain damaging and aging effects on the light emitting material layer 20, thereby reducing the luminous efficiency and lifetime of the display device. At the same time, in order to protect the second electrode on the light emitting material, it is necessary to form an auxiliary protective layer at the position where the auxiliary electrode is not provided before the auxiliary electrode is formed, and the auxiliary protective layer protects the second electrode from being damaged while the auxiliary electrode is being produced. However, this procedure is complicated and the contact between the auxiliary protective layer and the auxiliary electrode is not tight enough.
In a word, there is a need to improve the structure of the existing OLED display unit to solve the above problems.